The greatest challenge facing the integrated circuit industry is power dissipation, a problem understood by anyone using a laptop computer. Today's microprocessors can dissipate more than ten times the power density of an electric stove-top element. The underlying cause of this dissipation is the wasteful way in which information is handled in modern microprocessors. This project will investigate structures to improve two crucial parts of a computational system. In the first, devices will be developed for adiabatic reversible logic, using an approach that eliminates leakage power dissipation in digital logic. In this type of logic the energy used in the computation can be recovered and reused, instead of being lost to heat as in today's computers. However, in practice this recovery of energy is difficult to do in real systems. To address this, in the second thrust, power resonators will be developed that can efficiently recover and recycle the energy that is used to process information within the logic. Resonators coupled with reversible adiabatic capacitive logic can greatly reduce the power consumption of computing systems and increase the amount of computation that can be accomplished in an energy constrained application such as the internet of things (IoT). The outreach program proposed will target middle school and high school students through classroom activities involving faculty and graduate students, and field trips to bring students to the Notre Dame labs.
Power dissipation continues to be an immense challenge facing the integrated circuit industry, as today's microprocessors can dissipate more than 100 W/cm2, stretching the limits of single-chip cooling. The underlying cause of this dissipation is the wasteful way in which information is processed in modern processors. In conventional logic the energy used to encode a bit of information is dissipated to heat in each clock cycle. Adiabatic reversible logic can be used to lower dissipation by recovering and reusing the bit energies, but this approach is limited by the energy lost to leakage in the devices. In addition, energy recovery is complicated and often inefficient. The goal of this project is to develop micro-electromechanical systems (MEMS) structures for both crucial parts of a reversible computational system: logic and energy recovery. Reversible logic based on transistors is limited by the leakage through the transistors, but the MEMS-based adiabatic capacitive logic developed in this project eliminates leakage. The project will leverage work on devices such as nanorelays to produce voltage-controlled capacitors used in logic structures, and since current-carrying electrical contacts are not required, a key limitation of nanorelays is eliminated. Relatively little research has been done on power supplies that can drive the logic circuit then recover and reuse the energy used in the computation. Resonant circuits can meet these requirements, and this project will investigate MEMS resonators that operate with better efficiencies than are possible with on-chip inductor-based resonators. As a critical component for energy recovery, these resonators must have characteristics different that those of typical MEMS resonators, which are used mostly as time-bases for clocking, and for frequency filtering. The piezoelectric contour mode resonators developed here will deliver, and recover, significant energy into a capacitive load (the logic elements) with low internal dissipation. Resonators coupled with reversible adiabatic capacitive logic implement an overall system that can greatly improve the amount of computation that can be done in an energy constrained application such as IoT.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
